In the past, to obtain ion conduction between electrodes in secondary cells, fuel cells, dye sensitized solar cells, actuators, and other electrochemical devices, a liquid electrolyte comprised of an electrolytic salt dissolved in a solvent has been used. However, with a liquid electrolyte using a solvent, reduction in the amount of liquid along with time due to evaporation of the solvent or liquid leakage is liable to occur, so development of an alternative electrolyte has been studied.
As an alternative electrolyte to a liquid electrolyte using a solvent, utilization of a nonvolatile ionic liquid has been studied. For example, Patent Document 1 proposes an electrolyte composition which contains an imidazolium compound or a pyridinium compound which has an oligoether group as a substituent. By using such an ionic liquid as an electrolyte, the problem of the reduction in the amount of liquid along with time due to evaporation of the solvent or liquid leakage which is seen in a liquid electrolyte using a solvent can be improved. However, a liquid is still used as the electrolyte, so there are the problems that handling is not easy at the time of production of an electrochemical device and, further, the problem of liquid leakage at the time of use is not completely solved.
Therefore, use of a polymer material which is excellent in ion conductivity as an electrolyte (a so-called “polymer electrolyte”) has been studied. For example, Patent Document 2 proposes use, as an electrolyte composition, of a polyether compound which is comprised of a polyalkylene oxide main chain, ionic side chains, and counter ions of ionic side chains wherein the ionic side chains or counter ions exhibit liquid crystallinity. Further, Patent Document 3 proposes a solid electrolyte composition using a polymer compound which has cationic structures at the main chain or side chains and which has halide ions or polyhalide ions as counter anions of the cationic structures. These electrolyte compositions are solid in form exhibiting almost no fluidity in the normal usage environment of the electrolyte, so the problem of liquid leakage at the time of use of the electrochemical device is solved. Further, use formed into desired shapes by various shaping methods is possible, so compared with use of a liquid as an electrolyte, there is the advantage that handling at the time of production of an electrochemical device is easy.
However, there is the problem that the electrolyte composition which is described in Patent Document 2 and Patent Document 3 is not sufficient in ion conductivity. Further, it is a solid which exhibits almost no fluidity in the usual usage environment of an electrolyte, so preshaping is required to obtain the desired shape. There is also the problem that adjustment of the shape is difficult at the time of application to the electrochemical device. For this reason, a polymer material which has suitable fluidity to an extent enabling adjustment of the shape and further improved in ion conductivity is fervently desired.